Event

We study the signatures left by new light particles with a spin on the primordial cosmological fluctuations. In distinction from the pure de Sitter background, where fields with spin have to be massive enough to satisfy the Higuchi bound, the inflation allows to host spinning particles that are parametrically lighter than the expansion rate. I introduce the description of the particles with spin in the context of the Effective Field Theory of Inflation and discuss the main signatures left by such particles on the primordial fluctuations.